Solid forms, including polymorphs and co-crystals, exist in either amorphous or crystalline forms. In the case of crystalline forms, molecules are positioned in three-dimensional lattice sites. When a compound recrystallizes from a solution or slurry, it may crystallize with different spatial lattice arrangements, and the different crystalline forms are sometimes referred to as “polymorphs.” Further, a pharmaceutical co-crystal is a single crystalline solid that incorporates two neutral molecules, one being an API (Active Pharmaceutical Ingredient) and the other a co-crystal former. Co-crystallization alters the molecular interactions and composition of pharmaceutical materials. The different polymorph or co-crystal forms of a given API may differ from each other with respect to one or more chemical properties (e.g., dissolution rate, solubility), biological properties (e.g., bioavailability, pharmacokinetics), and/or physical properties (e.g., mechanical strength, compaction behavior, flow properties, particle size, shape, melting point, degree of hydration or salvation, caking tendency, compatibility with excipients).
Curcumin is a major constituent found in the spice tumeric, which is a dried powder from the rhizomes of Curcuma longa L. Several in vitro and in vivo studies demonstrated its suppression, retardation, or inversion of carcinogenesis. Some research also suggests that curcumin may help prevent or treat cancer. Furthermore, it also exhibits anti-inflammatory, antioxidant, antiviral, and anti-infectious activities and wound healing properties. Inhibition of arachidonic acid metabolism by curcumin has been suggested to be a key mechanism for its anticarcinogenic action. In addition, curcumin was found to inhibit herpes simplex virus 1 and 2 by controlling the immediate-early gene expression. However, curcumin has extremely poor water solubility and bioavailability. Because poor dissolution rate, solubility, chemical stability and moisture uptake influence therapeutic efficacy of many pharmaceuticals, and may therefore significantly lower the market value of a drug, there is a need to design new solid forms of curcumin for pharmaceutical use, such as polymorph or co-crystal forms of curcumin.